A media content provider or distributor may deliver various media contents to users using different coding schemes suited for different devices, such as televisions, notebook computers, and mobile handsets. An asset may comprise media content and metadata expressed as a media presentation description (MPD). The MPD may be an extensible markup language (XML) file or document describing the media content, such as its various representations, uniform resource locator (URL) addresses, and other characteristics. For example, the media content may comprise several media components (e.g. audio, video, and text), each of which may have different characteristics that are specified in the MPD.
Depending on the application, an asset or media content may be divided into various hierarchies. For example, the media content may comprise multiple periods, where a period is a time interval relatively longer than a segment. For instance, a television program may be divided into several 5-minute-long program periods, which are separated by several 2-minute-long advertisement periods. Further, a period may comprise one or multiple adaptation sets (AS). An AS may provide information about one or multiple media components and its/their various encoded representations. For instance, an AS may contain different bit-rates of a video component of the media content, while another AS may contain different bit-rates of an audio component of the same media content. A representation may be an encoded alternative of a media component, varying from other representations by bit-rate, resolution, number of channels, or other characteristics, or combinations thereof. Each representation comprises multiple segments, which are media content chunks in a temporal sequence.
In adaptive streaming, when delivering a media content to a user device, the user device may select appropriate segments dynamically based on a variety of factors, such as network conditions, device capability, and user choice. Adaptive streaming may include various equivalent technologies and/or standards, such as Dynamic Adaptive Streaming over Hypertext Transfer Protocol (HTTP) (DASH), HTTP Live Streaming (HLS), or Internet Information Services (IIS) Smooth Streaming. For example, DASH defines a manifest format, MPD, and segment formats for International Organization for Standardization (ISO) Base Media File Format (ISO-BMFF) and Moving Picture Experts Group (MPEG) Transport Stream under the family of standards MPEG-2, as described in ISO/International Electrotechnical Commission (IEC) 13818-1, titled “Information Technology—Generic Coding of Moving Pictures and Associated Audio Information: Systems.”
An MPD comprises various generic descriptors that describes or defines different levels of the media content. In MPD for DASH applications, generic descriptors such as supplemental property may be present on the adaptation set and representation levels, but not on the period level. Thus, when a period comprises more than one AdaptationSet, the descriptor needs to be repeated with each AdaptationSet, which may lead to inefficiency and/or inconsistency.